Drag reduction of hydrocarbon fluids flowing through conduits is well known. An example of such an operation is described in U.S. Pat. No. 3,626,676 which provides a method by which the percent drag reduction can be measured. The reference describes inserting the drag reducing additives as a polymeric liquid. Other representative art in the area includes U.S. Pat. No. 3,736,288 in which various drag reducing formulations are added to exhibit a staggered dissolving or controlled dissolving characteristic using varying molecular weight fractions and/or particle sizes. These materials are added as polymeric solids. The reference also discloses pumpability, pourability, stratification resistance, and the like of these solutions. U.S. Pat. No. 3,601,079 describes a water-soluble, polymeric material mixed with water in a mixing chamber prior to injection into a pipeline. U.S. Pat. No. 3,884,252 describes a process for reducing oxidative degradation and cold flow of polymer crumb by immersing the crumb in a non-solvent and then dusting prior to injecting the polymer crumb or slurry of polymer crumb and water into a hydrocarbon fluid and allowing the crumb to gradually and continuously dissolve throughout the pipeline. Injection of friction reducing polymers is also described in U.S. Pat. No. 4,263,929. A drag reducing dispersing metering system is described in U.S. Pat. No. 3,900,034.
There also exists a group of art relating to a method for dissolving polymers in solvent. This art does not specifically mention pipelining of fluids. This area of art is represented by U.S. Pat. Nos. 2,639,275; 3,468,322; 3,891,593, and 4,537,513. These patents all deal with methods for dissolving a fixed amount of polymer in a fixed amount of solvent, utilizing recycling or dissolving means. However, such methods of dissolving polymer require extra apparatus, and it would be highly preferable to directly inject drag reducing agents into a pipeline.
The performance of drag reducing additives is highly dependent upon the dissolution of these additives in the flowing liquid. Addition of solid materials to a pipeline and allowing dissolution as the material travels to the pipeline has not been found to be an effective means of promoting drag reduction, since the materials are not dissolved at the time during which they are needed to provide drag reducing effects. It has been found preferable to inject the materials in a dissolved state or in a highly viscous concentrate in order to promote drag reduction by the dissolution of the polymer.
It would therefore be of great benefit to provide a method and apparatus whereby high molecular weight drag reducing polymers can be introduced into fluids flowing through conduits in a manner to increase the performance of the drag reducing material.